Design and Construction Handbook - Los Angeles World Airports

Guide Specification
1. Calculate outside and return air enthalpy using measured temperature and relative
humidity; determine energy expended and control outside and return air dampers.
2. Operator commands:
a. Add/delete fan status point.
b. Add/delete outside air temperature point.
c. Add/delete discharge controller point.
d. Define discharge controller parameters.
e. Add/delete return air temperature point.
f. Add/delete outside air dewpoint/humidity point.
g. Add/delete return air dewpoint/humidity point.
h. Add/delete damper switch.
i. Add/delete minimum outside air.
j. Add/delete atmospheric pressure.
k. Add/delete heating override switch.
l. Add/delete evaporative cooling switch.
m. Add/delete air flow rate.
n. Define enthalpy deadband.
o. Lock/unlock program.
p. Request control summary.
q. Request HVAC point summary.
3. Control summary:
a. HVAC control system begin/end status.
b. Enthalpy switchover optimal system status.
c. Optimal return time system status.
d. Current outside air enthalpy.
e. Calculated mixed air enthalpy.
f. Calculated cooling cool enthalpy using outside air.
g. Calculated cooling cool enthalpy using mixed air.
h. Calculated enthalpy difference.
i. Enthalpy switchover deadband.
j. Status of damper mode switch.
2.9 PROGRAMMING APPLICATION FEATURES
A. Trend Point:
1. Sample up to 248 points, real or computed, with each point capable of collecting 8
samples at intervals specified in minutes, hours, days, or month.
2. Output trend logs as line-graphs or bar graphs. Output graphic on terminal, with each
point for line and bar graphs designated with a unique pattern or color, vertical scale
either actual values or percent of range, and horizontal scale time base. Print trend logs
up to 12 columns of one point/column.
B. Alarm Messages:
DIRECT-DIGITAL CONTROL SYSTEM FOR HVAC
23 09 23 - 16 Mechanical Systems